Over the past decade, the convenience of so-called "flip-top" cans equipped with a pull-type tab opening has enjoyed increasing popularity and has made them an established part of people's daily life in many countries. However, due to their inability of being resealable, flip-top cans have created a form of forced consumption by generating a substantial amount of unwanted waste. Once such a pull tab can is opened, its contents must be consumed within a relatively short period of time. Otherwise, the carbon dioxide in the case of carbonated beverage will escape and the beverage will consequently go "flat," thus becoming untasty and for all practical purposes unconsumable.
A similar situation applies to non-carbonated beverages, such as fruit juices. Unless the partially consumed contents of the can are properly sealed, the flavor and vitamin content escape as well in fairly short order.
There is an additional problem associated with flip-top cans which particularly affects children. As the metal tab is ripped off from the can top, it occasionally leaves some sharp burrs around the periphery of the opening. These burrs have been known to cause cuts and bleeding when the child's tongue is inserted into the pouring aperture of the can whether done inadvertently or in a playful way as the case usually is among youngsters.
While the prior art does not show to date any particular embodiment combining a spout an plug assembly allowing children to drink out of a flip-top can in total safety while preventing the carbon dioxide from escaping whenever desired, several reusable sealing arrangements for tab opening cans have been developed. Worthwhile as they are, seals of the kind currently available on the market fall short of the ideal embodiment for various reasons.
Several closures in the prior art, see U.S. Pat. Nos. 3,428,212; 3,622,034; 3,650,432 and Re. 27,301, are designed to fit only one specific type of opening geometry. Additionally, there is no provision for retaining the closures on the can so that reclosure is inconvenient for the consumer.
Other container closures and combination closure-dispensers not directly related to tab opening cans are disclosed in U.S. Pat. Nos. 2,986,309; 3,018,024; 3,021,976; 3,081,005; and 3,187,964.
The greatest difficulty involved in developing an effective sealing device for flip-top opening cans lies in the wide variety of their shape openings in terms of both dimensions and configuration.
Measurements of the opening geometry of all commercially available flip-top cans show that their lengths vary from 27 to 30 millimeters, their widths at mid-length vary by plus or minus 1 millimeter, whereas their maximum width at the base of the aperture ranges from 13 to 17 millimeters.
Consequently, to be effective, the sealing device must be sufficiently flexible and designed in such a way that it can conveniently contract lengthwise and especially widthwise while providing a tight and even peripheral seal regardless of the configuration of the opening and permitting at the same time ease of insertion and removal.